1. Field of the Invention
The present invention relates to a radiation imaging system and a radiation image detector.
2. Description Related to the Prior Art
In a medical field, a radiation imaging system, for example, an X-ray imaging system using X-rays is widely known. The X-ray imaging system is constituted of an X-ray source for applying X-rays to an object (patient) , an X-ray image recorder or detector for recording or detecting an X-ray image produced from the X-rays passed through the object, a source controller for controlling the operation of the X-ray source, a console for controlling the operation of the X-ray image detector, and an emission switch for inputting an emission start command of the X-rays.
In the X-ray image recorder, an X-ray film is used as a recording material. In the X-ray image detector, an imaging plate (IP) or a flat panel detector (FPD) is used as a detection panel. The IP has a base coated with an optically stimulated phosphor, which accumulates X-ray energy. The FPD has a matrix of pixels each of which accumulates signal charge in accordance with an X-ray dose received therein. The FPD accumulates the signal charge on a pixel-by-pixel basis, and converts the accumulated signal charge into a voltage signal in its signal processing circuit. Thus, the FPD detects the X-ray image of the object, and outputs the X-ray image in the form of digital image data.
The X-ray film or the IP is contained in a flat rectangular cassette body of a standardized size, and is used as a film cassette or an IP cassette, respectively. Likewise, an electronic cassette (portable X-ray image detector) that has the FPD contained in the cassette body is also in practical use. The electronic cassette is loaded not only in a specific imaging stand but also in an existing imaging stand designed for the film cassette and the IP cassette. Furthermore, the electronic cassette can be used while being put on a bed or held by the patient himself/herself, to perform imaging of a body portion that is hard to take in the imaging stand. The electronic cassette is sometimes brought out from a hospital for use in bedside radiography of a home-care patient or in an outside accident or natural disaster site in case of emergency.
A plurality of electronic cassettes are generally prepared in the hospital in consideration of the number of imaging stands, a backup, and the like. When performing imaging, one of the electronic cassettes is chosen appropriately. It is also often the case that an old electronic cassette is still used after the purchase of a new electronic cassette. Some doctors preferably use the film cassette or the IP cassette that was included in the imaging stand.
The development of the X-ray image detector has been made in order of the film cassette, the IP cassette, and the electronic cassette. The sensitivity of the detector is increased with the progress of the development, and the electronic cassette can detect a sharp X-ray image from a low dose of X-rays. Even among the cassettes of the same type, there is difference in the sensitivity and the like depending on the type of the X-ray film, the structure of the IP, or the structure of the FPD. Thus, an imaging condition has to be set optimally in accordance with the sensitivity and the like of the cassette to be used.
Japanese Patent Laid-Open Publication No. 2012-011207 discloses an X-ray imaging system in which an imaging controller receives information about sensitivity and the like from an X-ray image detector (X-ray sensor unit). An imaging condition including tube voltage, tube current, and a mAs value is automatically set based on the received information, and is displayed on a monitor. US Patent Application Publication No. 2004/0071263 discloses an X-ray imaging system in which the operating status of a plurality of X-ray image detectors is displayed on a monitor of a console.
To meet demands for higher sensitivity of the X-ray image detector, lower radiation exposure, and the like, it is required of a medical facility to perform X-ray imaging with as low a dose as possible. According to the Japanese Patent Laid-Open Publication No. 2012-011207, the display of the imaging condition is switched concurrently with a change of the X-ray image detector, so it cannot be judged that whether or not the chosen X-ray image detector is more suitable for low-dose imaging than the others. Also, when the X-ray image detector is replaced with a new one, a change of the displayed imaging condition may confuse a radiological technician.